You have some multimedia-model (Image/Audio) in your app. The actual files are stored on Amazon S3. And to tie these 2 together you use attachment_fu.
The problem you will have if you work in a team of developers is that, since attachment_fu is expecting one bucket per environment, all developers will write their data to that 'development'-bucket and possibly overwrite each others data.

A fast solution that does not involve hacking the plugin itself is to include this simple line in your model:

  CONFIG_PATH = RAILS_ENV == 'development' ?
        "#{RAILS_ROOT}/config/amazon_s3_dev.yml" : nil
 has_attachment :s3_config_path => CONFIG_PATH,
                              :storage => :s3,
                              .......

If you are in 'development' attachment_fu will look into amazon_s3_dev.yml otherwise into the default file amazon_s3.yml.
The advantage here is that you dont have to change the (probably version controlled) default config file.

The amazon_s3_dev.yml-file should then look sth. like this:

development:
  bucket_name: social_dev_your_name
  access_key_id: your_access_key_id
  secret_access_key: your_secret_access_key

You can now also remove the development entry from amazon_s3.yml.

Don't forget to create the actual buckets on s3 to complete this setup.